A compressor is a driven fluid machinery for promoting a low-pressure gas to a high-pressure gas and serves as the heart of a refrigeration system. It takes from an air intake tube a low-temperature and low-pressure refrigerant gas, forces down the piston to compress the gas under the drive of a motor, and then emits a high-temperature and high-pressure refrigerant gas to an air exhaust tube so as to supply a driving force to a refrigeration cycle. As such, a refrigeration cycle of compression→condensation (heat release)→expansion→evaporation (heat absorption) is realized.
A linear compressor is widely used in a device with a small refrigeration amount such as a refrigerator. It has advantages of a simple structure, less friction loss, low noise, convenient flow regulation through voltage regulation, more simple and reliable embodiment than frequency conversion regulation, and less use or no use of oil or lubricating oil, etc. A Chinese patent CN203394701U discloses a linear compressor. As shown in FIG. 1, it comprises two parts: a gas exhaust mechanism 1 and a compressor unit. The compressor unit comprises: a cylinder 16, a piston unit, a movable magnet linear oscillation motor, a resonant spring 8 and a compressor casing. The piston unit comprises: a piston 2, a piston rod 3, a rod end plate 10 and a suction valve 15. The gas exhaust mechanism 1 comprises an exhaust valve slice 17, an exhaust valve plate 18, etc.
A linear compressor is under electronic control during its running. When the output power is small, the stroke of the piston 2 in the linear compressor is relatively small. Thus, the piston 2 and the exhaust valve plate 18 can easily collide with each other, causing the compressor to fail. In light of this, when designing a frequency conversion plate of a linear compressor, people will set up a protection program to prevent damage to the mechanical components of the compressor. For example, the frequency conversion plate of the linear compressor will launch the protection program to stop the linear compressor from running.
When a refrigerator is running at a low temperature, the heat load of the refrigerator is relatively low, and accordingly, the refrigeration amount required by compartments is relatively low. In this case, the linear compressor will run with a lower output power, causing a small piston stroke in the linear compressor. As a result, a hidden danger of colliding with the exhaust valve plate by the piston exists.